RU2239698C1 - Method for preparing water for feeding into force wells - Google Patents

Abstract

FIELD: oil extractive industry.

SUBSTANCE: method includes supplying water-oil emulsion from product well consecutively to group measuring plant, first pump station, product park and cleaning plant, supply to second pump station and pumping into force wells. At territory of group measuring plant, first pump station and product park of dirt wells, barns and the like liquid is transported to utilization station. Additional filtration of liquid by filters is performed, with cell sizes 1-2 mm on mouth of force well which passed treatment of face area. Washing of rebuilt water ducts and force wells water ducts is performed, on which during last five years more than two maintenance procedures were performed or on which after last maintenance procedure no more than one year had passed. After treatment of face area of force well by mounting a mouth connecting pipe having diameter no more than 4mm until restoring pressure in face area and stabilization of well acceleration. On force wells with speed of back flow of liquid, enough for carrying out weighed particles along tubing pipes column from face during well stop, back valves are mounted.

EFFECT: simplified system for collecting oil and gas, higher reliability of said system.

1 ex

Description

The invention relates to the oil industry and may find application in the preparation of water for injection into injection wells.

A known system for collecting and preparing oil, which contains a node for measuring the production of wells, separators of the first and second stages, a hot separation stage, a preliminary water discharge tank with an intermediate layer intake unit with a pump and an intermediate layer pipe, on which a steam heater and a centrifugal phase separation unit are located, connected by a slurry line to a sludge collector and having oil and water outlet lines. The centrifugal separation unit is made in the form of biphasic decanter and three-phase plate centrifuges connected in series, the oil output line from the centrifugal separation unit is connected to the hot separation stage, and the water output line is connected to the reservoir pressure maintenance system (RF Patent No. 2094082, class B 01 D 17 / 04, publ. 1997.10.27).

The known method allows you to collect and prepare oil, however, incidentally produced water by this method must be disposed of.

Closest to the invention in technical essence is a system for collecting oil field products, including group metering units, booster pump stations with a water separator, cluster pump stations for maintaining reservoir pressure, oil and gas pipelines, sewage pipelines and a central collection point. The system is divided into several autonomous units containing a booster pump station with an inlet water separator and associated group metering units, and a cluster pump station with adjacent wells and pipelines. Oil from the booster pump station is transported together with gas by means of pumps for pumping a gas-liquid mixture (RF Patent No. 2159892, class F 17 D 1/00, publ. 2000.11.27 - prototype).

The technical result of the invention is to simplify the system of collecting oil and gas, increasing its reliability. However, the system does not provide the proper quality of water preparation for injection into injection wells.

The invention solves the problem of improving the quality of preparation of water for injection into injection wells.

The problem is solved in that in the method of preparing water for injection into injection wells, comprising supplying a water-oil emulsion from a production well in series to a group metering unit, to a booster pump station, to a commodity park and treatment facilities, to a well pump station and pumped into injection wells , according to the invention, in the territory of a group metering unit, a booster pump station and a freight fleet from liquid wells, barns and similar containers, the liquid is transported to the disposal point and, they flush newly constructed water conduits and water conduits of injection wells, where more than two repairs were made in the last five years or after 1 year or less after the previous repair, water pipes are washed after treatment of the bottom-hole zone of the injection well and the injection well is limited by the wellhead a fitting with a diameter of not more than 4 mm to restore pressure in the bottomhole zone and stabilize the injectivity of the well and conduct additional filtering of water at the mouth filters with mesh sizes of 1-2 mm, check valves are installed on injection wells with a liquid backflow rate sufficient to remove suspended particles through the tubing string from the bottom when the well stops.

The features of the invention are:

1) the supply of oil-water emulsion from the producing well sequentially to a group metering unit, to a booster pump station, to a commodity park and treatment facilities, to a well pump station and pumped into injection wells;

2) in the territory of a group metering unit, a booster pump station and a freight fleet, from the mud wells, barns and similar containers, liquid is transported to a disposal point;

3) flushing of newly constructed water conduits and water conduits for injection wells, in which more than two repairs have been carried out over the past five years or in which 1 year or less has passed after the previous repair;

4) after processing the bottom-hole zone of the injection well, flushing the water pipes;

5) the same and the limitation of the injectivity of the injection well by installing a wellhead fitting with a diameter of not more than 4 mm to restore pressure in the bottomhole zone and stabilize the injectivity of the well;

6) the same and conducting additional filtration of water at the mouth with filters with mesh sizes of 1-2 mm;

7) on injection wells with a reverse flow rate of liquid sufficient to carry suspended particles through the tubing string from the bottom when the well stops, installing check valves.

Sign 1 is common with the prototype, signs 2-7 are the salient features of the invention.

SUMMARY OF THE INVENTION

When developing waterlogged oil fields, a large amount of associated water is produced along with oil. This water, after appropriate preparation, is pumped into injection wells. With poor-quality water treatment, bottom-hole zones and injection wells themselves become contaminated. The injectivity of injection wells is reduced, which entails a decrease in reservoir pressure, a decrease in oil displacement, and a decrease in oil recovery. The proposed invention solves the problem of improving the quality of the preparation of water for injection into injection wells. The problem is solved as follows.

The extracted water-oil emulsion from the producing well is piped sequentially to a group metering unit, to a booster pump station, to a commodity park and treatment facilities, fed to a cluster pump station and pumped into injection wells. On the territory of a group metering unit, a booster pump station and a freight fleet, mud is transported from mud wells, barns and similar containers to a disposal point, and newly constructed water pipes and injection wells are flushed, which have completed more than two repairs in the last five years or after previous repairs took 1 year or less. After processing the bottom-hole zone of the injection well, the water conduits are washed and the injectivity of the injection well is limited by installing a wellhead fitting with a diameter of not more than 4 mm to restore pressure in the bottom-hole zone and stabilization of the injectivity of the well, and additional water is filtered at the wellhead with filters with mesh sizes of 1-2 mm. On injection wells with a rate of reverse fluid flow sufficient to carry suspended particles through the tubing string from the bottom when the well stops, check valves are installed.

Concrete example

The method is implemented in the reservoir pressure maintenance system of the Almetyevsk oil and gas production department of OAO Tatneft.

The contamination of oil pipelines occurs due to the pumping into the oil pipeline of the contents of earthen barns dug during the production of underground and major repairs of production wells.

To prevent this phenomenon, oil pipe risers are currently sealed at the mouth of the repaired production wells, preventing the contents of barns from being pumped into the oil pipeline.

The oil-water emulsion obtained from the producing well is piped to the group metering unit, where the produced fluid is recorded. After a group metering installation, the fluid is sent to a booster pump station.

On the territory of the group metering unit and the booster pump station there are mud wells and tanks that serve to bleed liquid from oil pipelines during the repair process, as well as to receive liquid from the spill sites at the site of gusts, barns, etc. Typically, liquid is pumped out of these mud wells into the oil gathering system, and dirt also gets there along with the liquid.

To reduce the ingress of contaminants into the oil gathering system, a wastewater recycling station has been equipped (well No. 16509). Wastewater from mud wells, tanks and barns is currently being transported to a disposal site. The ingress of such a liquid into the oil recovery system is not allowed. The wastewater disposal facility consists of two tanks of 200 m ³ each. The receiving tank is divided by a partition into two compartments. In the first compartment there is a hatch for receiving utilized water from water carriers. In this compartment, sedimentation of solid impurities contained in the drained liquid and separation of the emulsion into oil products and water occur. The dividing wall is mounted so that only waste water without oil products flows into the second compartment, and the remaining part of the petroleum products and smaller suspended particles remains in the second compartment and does not enter the second tank connected to the first tank by a jumper located in height in the middle of the tank. Coming into the second tank and already purified water contains suspended particles and oil products of not more than 50 mg / l.

The liquid thus purified from the second reservoir is pumped with an ETsNV 50 × 50 submersible pump to receive an inverted ETsN-125-1500 electric centrifugal pump mounted at the mouth of the injection well. This electric centrifugal pump pumps water into the reservoir. On average, the volume of utilized wastewater at this installation is 60 m ² / day. The ESP operates 12 hours a day.

Sources of contamination of the produced fluid during its movement from the producing well to the treatment facilities are bullets at group metering units and booster pump stations. Their cleaning also improves the quality of the fluid pumped into the injection wells.

To improve water quality, one direction was chosen, which includes 168 production wells, 5 group metering units and 2 booster pump stations. The total number of containers in this direction is 6 pcs. (V200 - 2 pcs., V50 - 4 pcs.). We cleaned all containers. After cleaning for 1 month, there are no peak surges due to the excess of oil products and the concentration of suspended particles in the water prepared for the reservoir pressure maintenance system (parameters regulated for the injection of oilfield wastewater: oil products - 60 mg / l, suspended solids - 50 mg / l).

From booster pumping stations, the extracted fluid is pumped to the freight fleet and treatment facilities. In case of violation of the preparation regime, oil products or solid particles can get into the water. The quality of the wastewater treatment is affected by the pollution of the tank farm at the treatment facilities of integrated oil treatment plants, the dead and intermediate layer of vertical steel tanks.

To improve the quality of wastewater treatment and to eliminate the effect of sewage on it, an integrated sewer system has been equipped in the workshops for complex oil treatment. This system provides for separate collection and disposal of sewage water, not related to the general wastewater treatment system. Sewage from the fleet and sewage treatment plants is collected in a separate sewer tank and then pumped using submersible pumps through a separate inlet conduit to the cluster pump station. There, sewage water is pumped by an individual pumping unit into disposal wells specially selected and prepared for such water into an absorbing layer. The presence of a separate sewer system made it possible to solve the problem of recycling the intermediate layer of vertical steel tanks and eliminated the harmful effect on the quality of the water treatment of polluted sewage

For continuous monitoring of the status of wastewater treatment at all product parks installed devices - signaling the presence of petroleum products in wastewater. For the experiment, the Severo-Almetyevsk Commodity Park was taken. This device is configured for the maximum permissible concentration (oil products - 60 mg / l, suspended solids - 50 mg / l) of oil products in wastewater using the actual sampling and analysis of samples for oil products. The readings of the device were displayed via a telemechanics system in the control room of the reservoir pressure maintenance shop. If the maximum permissible concentration of oil products in wastewater is exceeded, an alarm occurs on the dispatcher's console.

The next link in our chain is the cluster pump station itself and the water conduit leading to it.

It was found that the longer the operating life of the inlet conduit, the more various sediments accumulate in it. When testing sewage filters at various waste water pumping stations, it was found that the filters clog more often, where the inlet duct has a long service life.

Periodic cleaning of water mains or their washing was suggested.

It is known that in existing drainage tanks at cluster pumping stations, drainage is made from water pipelines during the elimination of gusts on them. From water pipelines, when they are poured out, solid suspended particles and oil products of various sizes and compositions fall into the drainage tank. Typically, when filling it, all this fluid is pumped out again to receive the pump and then to the injection wells. It was decided to clean the drainage tanks of the pumping stations.

In addition to this, unauthorized discharge of liquid after drainage, cleaning of the bottom-hole zone, etc., is carried out in drainage tanks. during the overhaul and underground well repairs. At the moment, drain covers of drainage tanks are protected from such drains by installing airtight manholes.

In order to effectively clean the water coming from treatment plants or freight parks, the presence of filters on the receiving lines of cluster pumping stations was not enough. The existing filters were a plate with holes up to 7-8 mm in diameter, i.e. they caught only very large solid particles and oil products, while the sizes of suspended solid particles in wastewater after treatment plants range from 50 microns to 2 mm. Own field studies were conducted to select the optimal design of the filters and the size of the filter elements. Studies were conducted for two injection agents: wastewater and fresh water. As a result, the gradation of cluster pumping stations with the required dimensions of the filter element in the directions of injection was determined. Depending on the state of the injection system (the duration of the operation of the water pipelines and what treatment facilities this cluster pump station works from), the size of the filter cell varies from 3 to 1.5 mm. For filters installed at the reception of fresh water pumping stations, the cell size ranges from 50 to 250 microns. As the pipelines and oil recovery systems are cleaned up and sewage is treated, the size of the filter cells decreases.

Another source of contamination of the injected water is the construction and existing pipelines of injection wells.

Field studies were conducted on new water pipelines to identify the degree and quality of pollution of water pipelines under construction. Measures have been developed to clean the lashes during the construction of a new water conduit.

According to existing water pipelines, criteria have been determined for the need for priority washing of water pipelines. The main criterion is the number of bottom-hole treatments on the injection well.

To reduce the initial number of flushing of existing water pipelines, water pipelines of those injection wells are washed, which have carried out more than two repairs over the past five years. If less than 5 years have passed after starting up the wells for injection, then the water pipes of those wells are washed, in which 1 year or less has passed after the previous repair and the current repair.

Using the selection criterion for pipelines for flushing, a priority list of existing pipelines for flushing is defined and implemented.

During operation, injection wells are periodically repaired. During the ongoing maintenance of wells in the barns, products of well flushing, residues of process fluids, etc. accumulate. All this was pumped either back into the water conduit and, as a result, again to the bottom of the injection well, or to a nearby oil gathering system. To avoid this, measures were taken to prevent fluid pumping into the linear part of the water conduits, providing for the installation of a seal on the linear part of the water conduit when the well was commissioned for repair.

Before performing a set of works on processing the bottom-hole zone, the well is stopped to reduce wellhead pressure. During this period and during the repair, the reservoir pressure in the area of this well decreases. As a result of this, when starting a well for injection, a large difference occurs between the wellhead and bottomhole pressure, the well has a high injectivity (a hungry well). Accordingly, a large flow of water carries dirt from the conduit into the bottomhole zone. As a result of this, the bottomhole zone is quickly clogged and the effect obtained from the treatment of the bottomhole zone is reduced. To neutralize this phenomenon for the period of well development after treatment of the bottom-hole zone, the increased injectivity of the well should be limited by the installation of a wellhead fitting. In this case, the diameter of the installed fitting should not exceed 3-4 mm.

The volume of fluid passing through the nozzle is measured by the formula

Q = m · S · (2 · (P ₁ -P ₂ ) / ρ) 1/2,

where m is the flow coefficient, depends on the configuration of the nozzle passage channel (for a cylindrical m = 0.71; for a converging cone m = 0.94); S is the area of the bore of the nozzle, m ² ; P ₁ -P ₂ - pressure drop across the fitting (Pa); p is the density of the injected fluid, t / m ³ .

The fitting is left for the entire period of well development after processing the bottom-hole zone, that is, until the bottom-hole zone of this well is saturated. At the time of saturation, stabilization of the injectivity of the well between two measurements during the development of the well is taken.

At the mouth of injection wells that inject wastewater and meet the criteria for selecting wells for flushing, it is necessary to install filters with mesh sizes of 1-2 mm. The installation of wellhead filters allows extending the overhaul period of the injection well before flushing the conduit.

In some of the injection wells with high pressure in the bottomhole zone, when the cluster pump station stops or when the pressure in the water conduit drops below a certain value, the fluid from the reservoir begins to overflow into other wells with lower wellhead pressure (sinking well). In this case, the casting liquid carries suspended particles and oil products from the bottomhole zone into the water conduit, polluting it. A certain amount of this mud is pumped into neighboring wells when starting a cluster pumping station. Check valves were installed at the mouth of these wells, which excluded this process. Installation of a non-return valve on all injection wells is not always justified, since a small flow of fluid between the wells when the injection is stopped at the cluster pump station in the winter period prevents the freezing of the wells. Therefore, it is necessary to install non-return valves only on those sinking wells where the rate of return fluid flow is sufficient to carry suspended particles along the tubing string from the bottom. For solid particles up to 2 mm - the velocity of the upward flow should be at least 0.5 m / s, for particles more than 2 mm - more than 0.5 m / s.

Implementation of the proposed method allowed to improve the quality of water treatment for the reservoir pressure maintenance system, reduce the number of bottomhole treatment zones of injection wells, and reduce the cost of maintaining reservoir pressure in the field.

Application of the proposed method will improve the quality of preparation of water for injection into injection wells.

Claims (1)

A method of preparing water for injection into injection wells, comprising supplying a water-oil emulsion from a production well sequentially to a group metering unit, to a booster pump station, to a commodity park and treatment facilities, to a well pump station and pumped into injection wells, characterized in that the territory of a group metering unit, a booster pump station and a freight fleet from mud wells, barns and similar containers, the liquid is taken to a disposal point, an additional water filtration with filters with mesh sizes of 1-2 mm at the mouth of the injection well that has undergone bottom-hole treatment is carried out by flushing the newly constructed water conduits and water conduits of the injection wells, which have completed more than two repairs in the last five years or have passed 1 year after the previous repair and less, after treatment of the bottom-hole zone of the injection well, water conduits are washed and the injectivity of the injection well is limited by installing a wellhead fitting with a diameter of not more than 4 mm to be restored I pressure near the wellbore and to stabilize the well injectivity of injection wells in with reverse fluid flow rate sufficient for the removal of suspended particles in the column tubing from the bottom with a stop borehole set check valves.